Role of opioid receptors in remifentanil-induced attenuation of renal ischemia/reperfusion injury in rats

Objective To investigate the role of opioid receptors in remifentanil-induced attenuation of renal ischemia/reperfusion (I/R) injury in rats.Methods Seventy-five male Sprague-Dawley rats weighing 250-300 g were randomly divided into 5 groups ( n =15 each):sham operation group (group S),group I/R,remifentanil group (group R),naloxone group (group N),and naloxone + remifentanil group (group NR).Renal ischemia was induced by clamping the bilateral renal arteries for 45 min using an atraumatic clamp followed by reperfusion.In groups R and NR,remifentanil was infused at 1.0 μg· kg-1 · min-1 via the caudal vein starting from 15 min before ischemia until 30 min of reperfusion,while groups S,I/R and N received the equal volume of normal saline instead of remifentanil.In groups N and NR,naloxone 0.3 mg/kg was injected via the caudal vein at 20 min before ischemia and at 35 min after ischemia respectively,while groups S,I/R and R received the equal volume of normal saline instead of naloxone.Blood and urine samples were collected from the femoral vein and urinary bladder respectively at 24 h of reperfusion for determination of the levels of serum creatinine (Cr) and blood urea nitrogen (BUN),urinary N-acetyl-β-D-glucosaminidase (NAG) and γ-glutamyl transpeptidase (γ-GT).The rats were sacrificed at 24 h of reperfusion and the renal tissues were removed for determination of nalondialdehyde (MDA) content and superoxide dismutase (SOD) activity.Pathological changes in renal tissues were observed with light microscope.Results Compared withgroup S,the levels of serum Cr and BUN,urinary NAG and γ-GT,and MDA were significantly increased,while the activity of SOD was significantly decreased in the other 4 groups ( P ＜ 0.05 or 0.01 ) and pathological changes in renal tissues were observed in the other 4 groups.Compared with group I/R,the levels of serum Cr and BUN,urinary NAG and γ-GT levels,and MDA were significantly decreased,while the activity of SOD was significantly increased ( P ＜ 0.01 ),and the pathological changes were reduced in group R,and no significant change was found in the parameters mentioned above in groups N and NR ( P ＞ 0.05).The pathological changes were similar in groups I/R,N and NR.Compured with group R,serum Cr and BUN concentrations,urinary NAG and γ-GT levels and MDA concent were increased,while SOD activity were decreased ( P ＜ 0.05 or 0.01 ).Conclusion Opioid receptors mediate remifentanil-induced attenuation of renal I/R injury in rats. Key words: Receptors, opioid; Piperidines; Kidney; Reperfusion injury